This invention relates to gear cutting machines and more particularly to mechanisms for truing disk-like abrasive tools used in a gear grinding machine tools for cutting straight bevel gears.
The invention may be advantageously used for truing abrasive tools in process of cutting fine-pitch straight bevel gears directly from heat-treated blanks hardened to a high degree of hardness (HRC 60-64) and without preliminary forming tooth spaces, as well as from blanks of steels not amenable to gear shaping or hobbing.
Known in the art are mechanisms for truing disk-like abrasive tools used in machine tools for cutting straight bevel gears with a single tool operating on a profile generating principle.
The conventional mechanism is mounted on a machine tool carriage mounting an abrasive tool and provided with truing elements driven from a self-contained drive means along paths corresponding to cutting profiles of the tool.
The truing elements comprise two levers each provided with a diamond truing tool. One of said diamond tools is used for truing taper and cylindrical active surfaces of the abrasive tool (active surfaces of the tool are those contacting surfaces being worked), while the other of said diamond tools is adapted for truing the face (or inactive) surface of the abrasive tool in case of changing the tooth module.
A mechanism for driving the lever with the diamond tool used for truing taper and cylindrical surfaces of the abrasive tool is enclosed into a separate housing which is stationary with respect to the carriage, said driving mechanism comprising a set of cams and templets having complex-shaped straightline, curvilinear and cylindrical surfaces. Said lever is arranged so that the diamond truing tool thereof is located in the region of contact between the abrasive tool and the tooth gear being machined, that is, in the working zone, while the feeding of said lever along with the diamond tool to compensate for the abrasive tool wear is carried out from the abrasive tool per se, the abrasive tool being mounted on a slide of the carriage.
The arrangement of the lever with the diamond tool in the working zone makes it impossible to perform truing of the abrasive tool without withdrawing the abrasive tool from the gear being machined.
It is necessary to stop the machine tool during its idle running, to shift the article being treated from the abrasive tool, to perform truing of the latter, to return the article into the initial position and only then to continue the operation.
All this reduces the efficiency of the machine tool, while periodic withdrawal of the article from the working zone impairs the accuracy of the straight bevel gears being manufactured due to possible displacement of the gear being machined with respect to the abrasive tool.
The other lever with the diamond tool for truing a face surface of the abrasive tool is also provided with a separate drive means in the form of a screw pair. This lever is mounted on an abrasive tool safety guard and set into motion by hand. This fact both is very dangerous to an operator and leads to a considerable loss of time resulted in a low machine tool efficiency.
Furthermore, the use of the conventional truing mechanism is limited since it is not suitable for truing abrasive tools having the periphery defined by three types of active surfaces, such as two taper surfaces and one cylindrical surface, the latter being confined between the former ones, the abrasive tool of the kind referred to being used for cutting fine pitch bevel gears without preliminary forming tooth spaces from blanks heat-treated to a high degree of hardness.